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The Nature of Matter Physical Sciences Benchmarks A. Describe that matter is made of minute particles called atoms and that atoms are comprised of even smaller components. Explain the structure and properties of atoms. B. Explain how atoms react with each other to form substances and how molecules react with each other or other atoms to form even different substance. C. Describe the identifiable physical properties of substances (e.g., color, hardness, conductivity, density, concentration, pH, and ductility). Explain how changes in these properties can occur without changing the chemical nature of the substance. H. Trace the historical development of scientific theories and ideas, and describe emerging issues in the study of physical sciences. Defining Matter Matter - anything that has mass and takes up space. Mass - the total amount of material in an object. Tool to measure - triple beam balance Units - mg, g, kg, etc. Defining Matter Volume - the amount of space an object occupies. The volume of liquids can be measured using a graduated cylinder or beaker. Units are liters (L) or milliliter (mL). The volume of irregular shaped objects are measured using water displacement with a graduated cylinder or beaker. Units are liters (L) or milliliter (mL). Defining Matter The volume of a cube can be calculated by measuring the length of one side using a meterstick or ruler. V = length X height X width Ex.: If the length of one side of a cube is 2 cm, what is the volume? V = 2 cm X 2 cm X 2 cm V = 8 cm3 Defining Matter Density - the amount of matter in a given space. D = mass / volume Mass and volume both need to measured separately! The calculation (ratio) of the two measurements equals the density. Ex.: If the mass of a cube is 54 grams and the length of a side is 3 cm., what is the density of the cube? First solve for volume: V = L X h X w V = 3cm X 3cm X 3cm V = 27 cm3 Density = mass = volume 54 g 27 cm3 = 2 g/cm3 Chemistry Elements - the building blocks of matter, a pure substance, made up of one type of atom. Atom - the smallest particle of an element that has the properties of that element. Substance - made up of one or more elements. Compound - a combination of two or more atoms that maintains its own properties. Molecule- smallest particle of a substance that retains all the properties of the substance and is composed of one or more atoms. Composition - what matter is made of and how it is organized Chemistry Properties - describes the characteristics, composition and behavior of matter, including the changes that matter undergoes. 1. Physical - characteristics that a sample of matter exhibits without any change in its identity. Solubility, melting point, boiling point, color, density, electrical conductivity, physical state. 2. Chemical - can be observed when there is a change in the composition of the substance. Iron at room temp with air = iron oxide (rust). Chemical formula- shows the number and kind of elements in a substance 2NH3 Coefficient (number of molecules) subscript (number of atoms) Classifying Reactions • Synthesis Reaction- Reaction in which two or more substances combine to form a compound. 2Na + Cl2 ------ 2NaCl • Decomposition Reaction- Compound breaks into two or more substances. 2HgO ------ 2Hg + O2 • Single Replacement Reaction- One element replaces another element in a compound to form a new compound Fe + CuSO4 ----- FeSO4 + Cu • Double Replacement Reaction- Occurs when two compounds in a reaction exchange ions AgNO3 + NaCl ----- AgCl + NaCO3 History Greek philosophers (Democritus) created theories about indivisible matter: “Atomos” - meaning that which cannot be cut or divided. Aristotle theorizes that everything is composed of Earth, Water, Air, and Fire. History Early 1800’s, John Dalton created the atomic theory: (4 parts) 1. All elements are made up of atoms. Atoms cannot be created, divided,or destroyed. 2. All atoms of the same element have the same size and mass. 3. Atoms of different elements have different sizes and masses. 4. During a chemical reaction, atoms are not destroyed, just rearranged. Nuclear power disproves theorem number one. (Fission and Fusion) Periodic Table History of the Periodic Table • Antoine LaVoisier 1790’s Complied a list of the 23 known elements at the time… • Most of the 23 had been known since as early as prehistoric times Cu, Pb, Au, Ag, Fe, C, S, Zn, Hg, As Sb, Cr, O, P History of the Periodic Table • Lothar Meyer(German)/ Dmitri Mendeleev (Russian) 1869 Noticed connection between atomic mass and properties Mendeleev gets more credit – he got published first- AND could better demonstrate the tables usefulness • Mendeleev was able to predict the properties of undiscovered elements The Periodic Table • Henry Moseley 1913 Found slight problems with Mendeleev’s periodic table Arranged elements in order of atomic number instead of atomic mass • Flip-flopped some elements (Ex – Cu and Zn) Resulted in clear patterns and properties www.chemicalelements.com/ The Periodic Table 3. Elements in columns are called groups or families a. Total of 18 groups b. Groups have same characteristic and # of valence electrons 1. Ve-: electrons in outer shell c. as elements descend atoms grow larger 4. Elements in rows are called series or periods a. elements are arranged by inc. # of protons (atomic #) b. Total of 7 periods c. Descending periods increase electrons in shells. This is due to increasing mass. d. As one goes across period atoms grow smaller.This is due to force of charge pulling in electrons. Atomic Mass and Numbers Atomic Number – number of protons Number of protons determines the number of electrons in a neutral atom. Atomic Mass – number of protons and neutrons Atomic mass minus atomic number equals the number of Neutrons. The Periodic Table Atomic Number 3 Symbol Li Name Lithium Atomic mass 6.941 Lithium Protons=3 Electrons=3 Atomic Mass=6.941 Neutrons=4 Element Sizes Electron Configurations These are the most stable arrangement of electrons There are 4 regions: s,p,d,f s holds total of 2 electrons ___ p holds total of 6 electrons ___ ___ ___ d holds 10 electrons ___ ___ ___ ___ ___ f holds total of 14 electrons ___ ___ ___ ___ ___ ___ ___ Shells will fill up one at a time (like seats on a bus) Electron Configurations • Most stable arrangement of electrons • 1s2 -The large number "1" refers to the principle quantum number "n" which stands for the energy level. It tells us that the electrons of helium occupy the first energy level of the atom. -The letter "s" stands for the angular momentum quantum number "l". It tells us that the two electrons of the helium electron occupy an "s" or spherical orbital. -The exponent "2" refers to the total number of electrons in that orbital or sub-shell. In this case, we know that there are two electrons in the spherical orbital at the first energy level. Oxygen: O 1s22s2 2p6 Bohr’ Models • Model that illustrates subatomic particles for an element Step 1: calculate total number subatomic particles Step 2: Create the nucleus by drawing protons and electrons Step 3: Create electron shells and attach the correct amount of electrons Step 4: Label all particles and shells Particle behavior Hund’s Rule: electrons are negative, they have same charge and repel from each other, as far apart as possible. Heisenberg Uncertainty Principle: 1920, impossible to measure accurately both the position and energy of an electron at the same time. Atomic Structure Subatomic Particles: the particles below the surface of an atom. This includes protons, neutrons and electrons. An electrical force between nucleus and electrons holds the atom together. atom: smallest particle of an element that has the chemical properties of that element. 1. a billion atoms laid end to end would make a line only 10cm long 2. atoms make up cells Atomic Structure A. electron: negatively charged particle orbits the nucleus 1. electron is first to be discovered - 1891 2. lightest subatomic particle B. proton: positively charged particle 1. located in nucleus of atom - 1896 2. second lightest subatomic particle C. neutron: neutrally charged particle 1. located with proton in nucleus - 1932 D. nucleus: holds protons and neutrons of atom 1. discovered in 1910 2. atoms are mostly empty space,distance between nucleus and electron is like a marble on the pitchers mound of a baseball field and the furthest seat in the stadium would be the electron. Atomic Models Electron Cloud Bohr’s Model